Jefferson Lab recognizes that magnets, and any associated
external fringe static magnetic fields, may be dangerous.It is therefore required that they be
controlled and the designated area provide warning of the potential hazards.This appendix defines Jefferson Lab’s minimum
engineering controls for this type of equipment; the administrative controls –
including area postings; and how these are updated, repaired, and maintained.

A
superconducting magnet quenches when most of its superconducting wire changes
to and remains in the non-superconducting state due to a rise in temperature or
exposure to excessive magnetic field.When called for by analysis, a system is installed to detect the quench
and trigger a lowering of the current and withdrawal of the stored magnetic
energy to preclude burnout of the conductor.Usually this system includes isolation contactor(s) and a diode/dump
resistor system.Quenches usually cause cryogen boil-off
and rapid current change, inducing voltages higher than the normal magnet
charging voltage. How the quench
protection system works and how hazards are mitigated are documented within the
magnet’s work control document.(See ES&H
Manual 6420 Appendix T2 Operational Safety Procedure for Qualifying Static
Magnetic Fields.)

This document is
controlled as an on-line file.It may be
printed but the print copy is not a controlled document.It is the user’s responsibility to ensure
that the document is the same revision as the current on line file.This copy was printed on 10/19/2012.